Porous inorganic siliceous materials including glass, ceramics, and silica gel are used as solid supports in chromatography, immunoassays, synthesis and other separation and purification procedures.
Gravitational and centrifuged separation of such porous materials from the surrounding medium when used in batch procedures such as immunoassays, is inefficient and time consuming. Centrifugal separations also require expensive and energy consuming apparatus.
Separation of magnetic solid supports is relatively easy and simple, especially for multiple, small aliquots of the kind frequently encountered in sample preparation and immunoassay procedures. Agitation of magnetic solid supports is readily accomplished by on and off switching of magnetic fields located at opposite sides of a container or simply shaken by hand. Non-porous metal oxide magnetic particles and magnetic polystyrene beads lack surface area necessary to provide high binding capacity.
Although there are quite a number of magnetic materials commercially available or reported in the literature, such as: iron oxide particles of U.S. Pat. Nos. 4,554,088 and 3,917,538; nickel oxide particles in Biotec. and Bioengr. XIX:101-124 (1977); agarose-polyaldehyde bead containing magnetic particles of U.S. Pat. No. 4,732,811. Commercial products such as: "DYNABEADS" (magnetic polystyrene bead); "MAGNOGEL 44" (magnetic polyacrylamide-agarose); "ENZACRY" (poly-m-diaminobenzene of iron oxide) reported in Clin. Chim. Acta. 69:387-396 (1976). Other types of magnetical particles reported in the literature include: cellulose containing ferric oxide, Clin. Chem. 26:1281-1284 (1980) and albumin magnetic microspheres, Ovadia, et al. J. Immunol. Methods 53:109-122 (1982).